A Temporally Explicit Production Efficiency Model for Fuel Load Allocation in Southern Africa

Abstract We present a regional fuel load model (1 km² spatial resolution) applied in the southern African savanna region. The model is based on a patch-scale production efficiency model (PEM) scaled up to the regional level using empirical relationships between patch-scale behavior and multi-source remote sensing data (spatio-temporal variability of vegetation and climatic variables). The model requires the spatial distribution of woody vegetation cover, which is used to determine separate respiration rates for tree and grass. Net primary production, grass and tree leaf death, and herbivory are also taken into account in this mechanistic modeling approach. The fuel load model has been calibrated and validated from independent measurements taken from savanna vegetation in Africa southward from the equator. A sensitivity analysis on the effect of climate variables (incoming radiation, air temperature, and precipitation) has been conducted to demonstrate the strong role that water availability has in determining productivity and subsequent fuel load over the southern African region. The model performance has been tested in four different areas representative of a regional increasing rainfall gradient—Etosha National Park, Namibia, Mongu and Kasama, Zambia, as well as in Kruger National Park, South Africa. Within each area, we analyze model output from three different magnitudes of canopy coverage (<5, 30, and 50%). We find that fuel load ranges predicted by the model are globally in agreement with field measurements for the same year. High rainfall sustains green herbaceous production late in the dry season and delays tree leaf litter production. Effect of water on production varies across the rainfall gradient with delayed start of green material production in more arid regions.     

Function and genetics of long versus short copulations in the cactophilic fruit fly,drosophila mojavensis (diptera: drosophilidae)

Variation in copulation duration of Drosophila mojavensisstrains was influenced by both sexes. Males maintained predominant control, as copulation duration of pairs from different strains was more similar to that of the strain from which the male was derived, but female origin also contributed significantly to the duration of copulation. Variation among strains was controlled by genes acting additively in both sexes. The size of both males and females also affected copulation duration. Small males copulated longer on average than large males, while males paired with large females copulated longer than those paired with small females. The importance of copulation duration to fitness was tested by correlation analyses with male size, female size, female remating latency, and number of eggs laid prior to female remating. Longer copulations stimulated earlier oviposition, possibly by increasing accessory gland secretions that are passed by males during copulation.     

Body size and area‐incidence relationships: is there a general pattern?

Aim This paper tests firstly for the existence of a general relationship between body size of terrestrial animals and their incidence across habitat patches of increasing size, and secondly for differences in this relationship between insects and vertebrates. Location The analysis was based on the occupancy pattern of 50 species from 15 different landscapes in a variety of ecosystems ranging from Central European grassland to Asian tropical forest. Methods The area‐occupancy relationship was described by incidence functions that were calculated using logistic regression. A correlation analysis between body size of the species and the patch area referring to the two given points of the incidence function was performed. In order to test for an effect of taxon (insects vs. vertebrates), an analysis of covariance was conducted. Results In all species, the incidence was found to increase with increasing patch area. The macroecological analysis showed a significant relationship between the incidence in habitat patches and the body size of terrestrial animals. The area requirement was found to increase linearly with increasing body size on a log‐log scale. This relationship did not differ significantly between insects and vertebrates. Conclusions The approach highlighted in this paper is to associate incidence functions with body size. The results suggest that body size is a general but rather rough predictor for the area requirements of animals. The relationship seems valid for a wide range of body sizes of terrestrial animals. However, further studies including isolation of habitats as well as additional species traits into the macroecological analysis of incidence functions are needed.     

The precursor of interleukin-1 alpha is phosphorylated at residue serine 90

Mononuclear phagocytes release interleukin-1 (IL-1), a 17-kDa polypeptide with diverse biological activities. IL-1 is synthesized as a precursor (31 kDa) which lacks a signal sequence or hydrophobic domains that could facilitate transmembrane translocation. Possible postsynthetic modifications of IL-1 that might account for its cellular transport were examined. We found that lipopolysaccharide stimulated, but not unstimulated, murine macrophages incorporated 32PO4 into the IL-1 alpha precursor (31 kDa) predominantly at residue serine 90. Released IL-1 alpha (17 kDa) is not phosphorylated in agreement with peptide sequence data that the site of 32P incorporation is in the amino-terminal one-third of the precursor. Approximately 10% of the phosphorylated IL-1 alpha precursor is membrane bound and associated with a fraction enriched in lysosomal vesicles. Together these data suggest mechanisms by which the postsynthetic proteolysis of the IL-1 alpha precursor may be modified and cellular transport of IL-1 alpha is accomplished.     

Aphanizomenon ovalisporum (Forti) in Lake Kinneret, Israel

The filamentous cyanobacterium Aphanizomenon ovalisporum wasobserved for the first time in Lake Kinneret in August 1994and formed a prominent bloom from September through October.Aphanizomenon ovalisporum reappeared in diminished amounts inthe summer and fall of 1995. These events are the first recordof significant quantities of a potentially toxic nitrogen-fixingcyanobacterium in this lake. No definite provenance of inoculumhas been identified, although A.ovalisporum was also observedin a newly reflooded area (Lake Agmon) in the catchment. Unusuallyhigh water temperatures and low wind inputs were observed priorto and during the A.ovalisporum bloom period. These, togetherwith possibly enhanced availability of phosphorus or other growthfactors, may have contributed to the cyanobacterium growth in1994. Phosphorus limi tation, as indicated by high cellularalkaline phosphatase activity, the onset of stormy conditionsand a fall in water temperatures led to the demise of the 1994bloom. Although the A. ovalisporum bloom in 1994 had no seriousdirect impact on water quality, the continued presence of apotentially toxic cyanobacterium in Lake Kinneret, a major nationalwater supply source, is a cause for serious concern.     

High affinity specific antiestrogen binding sites are concentrated in rough microsomal membranes of rat liver

Saturation and competitive binding analyses demonstrated the presence of a high affinity (K_D = 0.92 nM), specific antiestrogen binding site (AEBS) in rat liver microsomes and at least 75% of total liver AEBS was recovered in this fraction. When microsomes were further separated into smooth and rough fractions, AEBS was concentrated in the latter. Subsequent dissociation of ribosomes from the rough membranes revealed that AEBS was associated with the membrane and not the ribosomal fraction. Antiestrogen binding activity could not be extracted from membranes with 1 M KCl or 0.5 M acetic acid but could be solubilized with sodium cholate. These data indicate that AEBS is an integral membrane component of the rough microsomal fraction of rat liver.     

Lens regeneration from cultured newt irises stimulated by retina-derived growth factors (EDGFs)

It has been shown that lens regeneration from the iris of the newt Notophthalmus viridescens is dependent on the presence of neural retinal tissue in organ culture and in vivo. The recent discovery of various eye-derived growth factors (EDGFs) in the bovine retina [14] prompted us to investigate whether one of these factors may be involved in the stimulation of lens regeneration. Dorsal irises were cultured for 20 days in serum-supplemented diluted Eagle's medium. Growth factors from bovine retina of various degrees of purification were added. Lens regeneration was assessed on the basis of morphological lens-regeneration stages and by immunofluorescent detection of a lens-specific marker protein, alpha-crystallin. Crude isotonic retinal extract at 80-800 micrograms/ml significantly augmented lens regeneration. Very similar results were obtained when EDGF III, the nonretained retinal factor after heparin-affinity chromatography, was present at 2-20 micrograms/ml. Lens regeneration was also significantly increased when EDGF II, the retinal form of acidic fibroblast growth factor (aFGF) at 50-500 ng/ml was added to the cultures. On the other hand, EDGF I at 4-40 ng/ml and brain basic FGF at 5-50 ng/ml did not seem to significantly stimulate lens regeneration under the conditions used. Our results suggest that at least two retina-derived growth factors (EDGF II and III) can stimulate lens regeneration. These growth factors may be the putative signal that is naturally produced by the retina during lens regeneration in the newt.